1. Field of the Invention
The present invention relates to low temperature deposition of phase change memory materials, by deposition techniques such as chemical vapor deposition and atomic layer deposition, to form microelectronic device structures.
2. Description of the Related Art
Phase Change Memory (PCM) refers to a novel memory technology based on chalcogenide materials that undergo a phase change via a heater and are read out as “0” or “1” based on their electrical resistivity, which changes in correspondence to whether the phase change material in the cell is in the crystalline or amorphous phase.
The chalcogenide materials used in PCM comprise a large number of binary, ternary, and quaternary alloys of a number of metals and metalloids. Examples include GeSbTe, GeSbInTe, and many others. As contained herein, the identification of compounds such as GeSbTe and GeSbInTe without appertaining stoichiometric coefficients or values will be understood as a general representation inclusive of all forms of such compounds containing the specified elements, and inclusive of all appertaining stoichiometric coefficients and values. For example, the reference to GeSbInTe includes Ge2Sb2Te5, as well as all other stoichiometric forms of such compound GeSbInTe.
PCM devices require relatively pure chalconide material alloys, with well controlled composition. Current processes for making PCM devices utilize physical vapor deposition to deposit thin films of these chalconide materials. The thick planar structures of the current generation are well-served by PVD.
As device geometries shrink, the chalconide material must be deposited into vias in order to control the phase transition and the necessary heat transfer. Such implementation of chalconide materials can also be beneficial in improving reliability of small volume devices.
A major deficiency in the current art is the requirement of high deposition temperatures needed for conventionally employed alkyl (e.g., Me3Sb, Me2Te) or halide sources. These temperatures are typically well in excess of 300° C., and may for example be on the order of 500° C. Such high temperatures substantially exceed the thermal budget for device integration and can result in the evaporation of the chalcogenide, rendering the product PCM device deficient or even useless for its intended purpose.
The art continues to seek improvements in the art of PCM devices, including improvements in manufacturing techniques and improved precursors useful for forming memory device structures.